Process of dehydrating sodium-sulfate crystals.



J. DAVIS. PROCESS OF DEHYDRATING SODIUM SULFATE CRYSTALS.

APPLICATION FILED AUG. 6, 1910.

Patented Apr. 18, 1911.

fa/om 1741 165,

PATENT OFFICE.

JOHN DAVIS, OF LARAMIE, WYOMINGcQ v PROCESS OF DEHYDRATINGSODIUM-SULFATE QRYSTALS.

ming, have invented new and useful Improvementsin ProcessesofDehydrating Sodium-Sulfate Crystals, of which the following is aspecification.

This invention relates to a process of dehydrating and utilizing.natural hydrated sulfate of soda in the manufacture of glass and in theproduction of other sodium salts,

such as caustic soda, carbonate of soda, sal' soda, bicarbonate of soda,etc.

The natural sulfate of soda referred to is a hydrate found in largequantities in \Vyomin'g and other sections of the United States, andconsists of a highly pure crystallized sodium sulfate containing from50% to of water. At a temperature of from 100 to 150 F. the crystalsdissolve in their water of crystallization, forming a liquid which mustbe stored against loss in stout iron vessels, and which cannot becommercially used in any of the customary ways. Attempts have been madeto render this substancecommercially available by a drying out processin reverberatory furnaces and subsequently calcination, but this processhas been found impracticable on account of. its prohibitive cost.

The object of the present invention is to provide a'process whereby suchnatural sulfate of soda/may be easily and economically dehydrated andrecovered or used in the manufacture of glass or in the production ofany of the sodium salts made from sodium sulfate.

In the accompanying drawings :Figure 1 is an elevational View, partiallyin section, of a form of apparatus which may be used in carrying myprocess into practice. Fig. 2 is a to plan view of the drier. Fig. 3 15a longitu inal section through the drier. Fig. 4 is a transverse sectionthrough one of the drier sections.

Referrin to the drawing for a more complete description of theapparatus, 1 designates a drier comprising a longitudinal trough of anydesired length and consisting of a series of sections placed end to endand suitably coupled together. In the present illustration, the drier isshown as composed of three sections 2, 3 and 4, each approximately ofsemi-circular form and composed of spaced semi-circular plates -5 and 6,the

munication with each other.

Specification of Letters Patent: Patented Apr, 18, 1911, Applicationfiled August 5, 1910. Serial No. 575,667.

inner section 5 forming a channel to receive the material to be driedand the outer section 6 an external steam space, chamber or jacket 7,closed at its top and ends in any suitable manner. The outer end of theprimary sec 'tion 2 is closed by an end wall 8 against the escape ofmaterial at this .point, and the abutting ends of 'tlie'sections areflanged and bolted or riveted together so that while the channels of thesections will communicate to form the longitudinal trough or passage thesteam chambers or jackets of the several sections will be closed againstcom- The rear or delivery section 4 is provided with a delivery chute 9,andjthe" inlet end of the steam jacket of each sect-ion is incommunication with asteam supply pipe 10 having a controllin valve 11,while the rear or delivery end of each section is provided with anoutlet 12 for the exhaust of the steam and water of condensation, whichoutlet may be check-valved toconfine the steam to a determined degree sothat as large a proportion of theheat as possible may be utilized.

Arranged adjacent the primary section of the drier is a suitable mixer13 having a (lelivery spout 14 disposed to discharge the mixed materialinto the buckets 15 ofa conveyer 16, by which the material is elevatedand discharged through a chute 17 into a supply bin 18 having an outlet19 controlled by a suitable gate 20. The material discharging throughthe outlet 19 passes into an automatic feeder 21, by'which the materialis'deposited into the primary section of the drier. Arranged within thedrier is a combined mixer or agitator and feeder 22 by which thematerial is fed along the trough from the primary to the deliverysection and discharged through the outlet 9, and by which the materialin its passage is also thoroughly agitated or stirred'and loosened up soas to be effectually heated throughout on its passage through the drierto evaporate the moisture contained therein. The discharge chute 9 isarranged to deliver the dried material into the buckets 23 of a conveyer24, whereby the dried material is elevated and discharged through achute 25 into a storage bin 26 having an outlet 27 controlled by a gate28, from which bin the material may be returned to the primary sectionof the drier to be subjected-to a second course of drying or dischargedinto the furnace for conversion into glass or one of suitable amount ofhydrated sulfate of soda is combined in the mixer 13 with a properproportion ofsolid, comminuted porous or absorbent vehicle, which is fedin the described manner to the primary section of the drier and thenthrough the drier by the action of the feeder 22. As the mixture passesthrough the drier the mass is thoroughly agitated by the feeder andheater to constantly higher degrees by the steam jackets, whereby thewater contained in the "mass is gradually evaporated until when themixture is ready for discharge through the outlet 9, all the moisture isexpelled the mixture as a Whole thoroughly dried and the sulfate of sodahydrated. It will be understood that under the comparatively lowtemperature of heat in the primary section 2 of the drier, the crystalsare dissolved in their water of crystallization,

forming a fluid which would otherwise be difficult to treat, exceptunder very high temperatures, for the expulsion of the moisture, but bycommingling this fluid with a solid, comminuted porous or absorbentvehicle, the fluid is distributed throughout the mass of the vehicle,and may consequently be more readily evaporated, so that at thecompletion of the course of drying treatment a solid mass will be left,consisting of the vehicle and dry or dehydrated sodium sulfate crystals.At this stage the dehydrated sodium sulfate may be separated from thevehicleby a dry or chemical process of. separation in any suitable way,and any suitable vehicle for this purpose may be employed, but I preferin practice to combine the hydrate with a vehicle consisting oftheingredients which are to be employed therewith for conversion underfusion into glass or one of the sodium salts ordinarily made from sodiumsulfate, so that through one and the same course of treatment thehydrate may be dried or dehydratedgand the components of the vehiclealso properly dried to'prepare the mass for introduction into the.conversion furnace without subseing of sand and lime or any of the othermaterials commonly used in combination temperature suflicientl dratingsodium sulfate crystals, which consecure with soda forthe production ofa batch. A combination of sand in the proportion of 100 lbs, to 35lbs.of-lime and &0 lbs. of the previously ground hydrate provides aneflicient mixture, the quantity of hydrate being doubled over a processemploying dehydrated sulfate of soda, to make allowance for about 50%,by weight, of moisture. Through the course of treatment described themoisture contained in the mass will be expelled, forming a charge readyfor the furnace into which it'may be: directly introduced withoutfurther treatment. It will thus be seen that the vehicle used performsthe double service of a carrier for holding and distributing the.moisture so that it can be readily evaporated and as elements which willchemically combine with the soda for the production of glass. In thepreparation of the hydrate for conversion into any of theother salts ofsodium, the vehicle may similarly consist of those ingredient-s commonlycombined under fusion with sulfate of soda for its conversion into thede-, a.

sired salt. As anexample, in the pro'duc- 90 tion of a black ball batchfor the manufacture of carbonate of soda, the vehicle may consist oflime stone and fine coal which may be mixed with the previously groundhydrate in the proportions (for an ordinary revolving furnace) of 28hdt. of the lime of stone to 19 hdt. of the coal and 30 hdt. of thehydrate, proper allowance being made for the amount of moisturecontained in the last. By subjecting this mixture to the drying actiondescribed, the moisture will be expelled and the mixture will then beready for introduction into the carbonating furnace.

It will accordingly be understood that by means of my process naturalhydrated sulfate of soda containing a high percenta e of moisture may bemade commercial y available at a comparatively low cost and thatthe'process may, as a matter offact, be employed in lieu of the usualprocess of drying the sand or any of the other vehicular ingredientsprior to use.

' Having thus described the invention, I claim: e

1. The herein-described process of dehydrating sodium sulfate crystals,which consists in admixing'the crystals with a porous vehicle of acharacter incapable of dissolvin in the melted crystals at temperaturessu cient to evaporate the moisture and in quantit suflicient. to preventtheformation of a fluid mass when heated at such temperatures, agitatingthe mixture, and heating the mixture while under constant agitation at ahigh to evaporate the moisture and sufiiclently low to prevent themelting of the vehicle.

2. The herein-described processof dehysists in admixingthe crystals witha porous vehicle of a character incapable of dissolving in the meltedcrystals at temperatures sufficient to. evaporate the moisture and inquantity sufficient to prevent the formation of afluid mass when heatedat such temperatures, agitating the mixture, and heating the mixture togradually increasing temperatures while under constant agitation to adegreesufficiently high toevaporat the moisture and sufficiently low toprevent the melting of the vehicle.

3. The herein-described process of dehydrating sodium sulfate crystals,which consists in admixing the crystals with a solid comminutedabsorbent vehicle of a character incapable of dissolving inthe meltedcrystals at temperatures sufficient to evaporate the moisture and inquantity sufficient to prevent the formation of afluid mass when' heatedatsuch temperatures, conveying the mixture through a course of travel,and heating the mixture along its path of travel at a temperaturesufficiently high to evaporate the moisture and sufficiently low toprevent the melting of the vehicle.

4. The herein described process of dehydrating sodium sulfate crystalswhich consists in mixing the crystals with a porous vehicle of acharacter. incapable of dissolving in .the melted crystals attemperatures sufficient to evaporate the moisture and in quantitysufficient to prevent the formation of a fluid mass when heated at suchtemperatures, conveying the mixture through a ourse of travel, stirringor agltatmg the mixture during its course of travel, and heating themixture during its course of travel at a temperature sufficiently highto drating sodium sulfate crystals, which contating the mixture duringits course of travel ata temperature sufficiently high to evaporate themoisture and sufficiently low to prevent the melting of the vehicle.

6. The herein-described process of dehydrating sodium sulfatecrystals'and preparing the same for use in the production of anothersubstance, which consists in mixing I l f the crystals with an absorbentvehicle incapable of melting and dissolving in the melted crystals attemperatures sufficiently low to evaporate the moisture and in quantitysufficient to prevent the formation of a fluid mass when heated at suchtemperatures but capable of melting and chemically combining with thedehydrated crystals at relatively higher temperatures to form the de--low to evaporate the moisture and in quan-- tity sufficiently great toprevent the formation of a fluid mass when heated at such temperaturesbut capable of melting and chemically combining with the dehydratedcrystals at relatively higher temperatures to form thedesired substance,conveying the mixture through a course of travel, and subjecting themixture during its course of travel to heat below the melting point ofthe vehicle but sufficiently high to evaporate the moisture from themixture.

3. The herein-described process of dehydrating sodium sulfate crystalsand preparing the same for use in the production of another substance,which consists in mixing the crystals with a solid comminuted absorbentvehicle incapable of melting and dissolving in the melted crystals attemperatures sufficiently low to evaporate the moisture and in quantitysufficiently great to prevent the formation of a fluid mass when heatedat such temperatures but capable of melting and chemically combiningwith the dehydrated crystals at relatively higher temperatures to formthe desired substance, conveying the mixture through a course of travel,agitating it in its course of travel,

- and subjecting the mixture during its course of travel to heatbelowthe melting point of the vehicle but sufficiently high to evaporate themoisture from the mixture.-

In testimony whereof I affix my signature 7 in presence of twowitnesses.

JOHN DAVIS.

Witnesses B. F. MILLER, C. D. SPALDING.

